Why are my surface materials distorted?
It's an issue with the model of the containers. That strange artifact is in fact 2 faces ocuppying the same space. You have made several different objects and some have overlapping faces between different objects and even with it self. You should do retopology on your model, by just 2 objects: the outer container and the inner container. After you create just this retopologized objects, do the modifiers. You have to check that all edges are well connected, no double vertices, no existance of non-manifold elements.